JP2003-070179A, published by the Japan Patent Office in 2003, proposes a monitoring device that detects a voltage of each unit cell in a plurality of battery modules, each of which comprises a plurality of unit cells.
The monitoring device comprises integrated circuits (IC), each of which detects voltages of the unit cells in each of the battery modules. These integrated circuits are connected to a controller via a so-called cascade connection circuit, and information output from each integrated circuit is processed in the controller. The monitoring device comprises an entire output voltage detection circuit for detecting an entire output voltage of the battery modules and is configured to determine a state of the battery modules through a process of comparing the data obtained from the integrated circuits and the data obtained from the entire output voltage detection circuit.